How to make joints for 3D printing?
I think the quickest and probably easiest thing for you to do is as you said cut the joints in Blender and instead of making a hinge system make a pin system. So basically what i am saying is have like 2 parts with 2 holes which align in the right position and then just slide a 3D printed pin/Cylinder into it. This would allow you to move along a certain axis. However if you wanted something that could be rotated fully then i would suggest a ball and clasp type system. Now this could be trickier for the fingers but would almost certainly work for the hand to arm joint.

Hope this helps!